Use Of Digital Holographic Interferometry Research Articles

Quantitative measurement of thermal lensing in diode-side-pumped Nd:YAG laser by use of digital holographic interferometry

Thermal lensing in diode-side-pumped Nd:YAG laser has been measured quantitatively using digital holographic interferometry. A series of holograms, carrying the information of the laser rod under different pump currents, are recorded with a CCD and reconstructed numerically. The optical path difference induced by the thermal lensing and the corresponding evolution process under different currents are obtained accordingly. Further, the thermal lensing diopters, induced aberrations, and its Zernike coefficients are calculated. The proposed method can be applied in the thermal lensing measurement and the optimization design of a laser resonator.

Optical diagnostics of the process of free liquid convection

A technique for complex investigation of the process of free liquid convection under the action of a heat source is presented, which is based on the use of digital holographic interferometry. The mode of studying an object, which is a flat liquid layer in a glass cell, has been developed. Experimental results have been obtained in the form of space–time temperature distributions for water, glycerol, and a mixture thereof. A dominant mechanism of heat transfer in different stages of heating the liquids under study has been revealed. A mathematical model of the process of free convection is constructed and the space–time temperature distribution is calculated for the case in which water is used as a test object. The results of mathematical simulation correctly describe the experimentally observed character of changes in the thermal field.

Digital holographic testing of biconvex lenses

Lenses are one of the most important optical elements for manipulation of wavefronts. For their proper selection, the wavefronts produced by the lenses should be analyzed. Digital holography is a tool which provides whole-field reconstructions of wavefronts, and here the use of digital holographic interferometry in complete characterization of wavefronts from lenses is investigated. Digital holograms of the wavefront from the test lens are recorded for various positions of the test lens from a point source. The reconstructed phase of the wavefront from the test lens is compared with a digitally inputted wavefront for measurement of parallelism as well as curvature. The focal length of the test lens is computed by measuring the change in curvature of the wavefront for two positions of the test lens. The radius of curvature of the test lens is determined by using the test lens in the reflection mode. Refractive index of the lens material is also determined using this method. Detailed theoretical and experimental analysis is provided.

Digital holographic interferometer using simultaneously three lasers and a single monochrome sensor for 3D displacement measurements

The use of digital holographic interferometry for 3D measurements using simultaneously three illumination directions was demonstrated by Saucedo et al. (Optics Express 14(4) 2006). The technique records two consecutive images where each one contains three holograms in it, e.g., one before the deformation and one after the deformation. A short coherence length laser must be used to obtain the simultaneous 3D information from the same laser source. In this manuscript we present an extension of this technique now illuminating simultaneously with three different lasers at 458, 532 and 633 nm, and using only one high resolution monochrome CMOS sensor. This new configuration gives the opportunity to use long coherence length lasers allowing the measurement of large object areas. A series of digital holographic interferograms are recorded and the information corresponding to each laser is isolated in the Fourier spectral domain where the corresponding phase difference is calculated. Experimental results render the orthogonal displacement components u, v and w during a simple load deformation.

Diffusivity studies of transparent liquid solutions by use of digital holographic interferometry

Real-time digital holography is used to study the diffusion process in transparent liquid solutions. Holograms of an object diffusively reflecting through an experimental cell containing diffusing solutions are recorded at different time instances. The recording medium is a CCD chip. The holographic interference of the object at two time instances is carried out numerically in a PC and is used to determine the diffusion coefficient. Holographic interferometric fringes can be displayed on a PC monitor in near real time. The software developed for this method determines the diffusion coefficients automatically. The calculated diffusion coefficients obtained with this method matched well with literature values.